Evolution of Iron Metabolism Genes and their Association with Ectoparasitism in the Calliphoridae Family

• Grant number: 25/26717-6
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: January 01, 2026
• End date: December 31, 2026
• Field of knowledge: Biological Sciences - Zoology
• Principal Investigator: Tatiana Teixeira Torres
• Grantee: Leandro Afeltro de Melo
• Host Institution: Instituto de Biociências (IB). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Associated research grant: 25/12518-1 - Genetic and evolutionary origins of trophic specialization in blowflies: mobile elements and metabolic pathways in a phylogenetic context, AP.R

Abstract

One of the major challenges in evolutionary and molecular biology is understanding the genetic mechanisms underlying the evolution of complex traits. Behavioral traits, such as feeding habits, are highly plastic and influenced by environmental, physiological, and genetic factors. As an example, classical studies in Drosophila melanogaster have enabled the identification of genes directly associated with behaviors such as aggressiveness (fruitless), courtship (courtless), and circadian rhythms (period).In the context of the evolution of feeding habits, the family Calliphoridae (Diptera) represents a promising model. Their larvae display two main habits: necro-saprophagy (with larvae that feed on decomposing organic matter) and parasitism (infesting the living tissues of vertebrates). Parasitism may be obligatory or facultative and represents a derived condition from necro-saprophagous ancestors. This transition involves constant exposure to iron-rich environments, such as the host's blood.Iron is essential for numerous cellular processes but can also generate highly toxic hydroxyl radicals, requiring refined homeostatic mechanisms. The iron-regulation system is well known in mammals and yeasts but remains poorly understood in insects. In D. melanogaster, for example, ferritin plays a central role in iron sequestration and protection against its toxic effects. Suppressing ferritin expression causes iron accumulation in ocular and neuronal cells, leading to deformities. When exposed to iron-rich diets, these insects increase ferritin transcription, suggesting an adaptive role. Two recent studies suggest a functional association between iron-metabolism genes and parasitism in calliphorids. Previous studies identified increased expression of the gene Malvolio, a co-transporter of iron and copper, in parasitic species. In a broader study, increased expression of ferritin genes was observed in parasites of the superfamily Oestroidea. These data suggest that constant exposure to high iron levels during feeding may have selected for specific molecular adaptations.Thus, this project proposes to identify and characterize genes involved in iron metabolism in calliphorid genomes, test hypotheses of positive selection in these genes, and investigate their expression in larval and adult stages using already published RNA-seq data. To achieve these objectives, the scholarship holder must (1) identify genes annotated with GO terms associated with iron metabolism in the Lucilia cuprina genome; (2) search for orthologs of these genes in 18 Calliphoridae genomes with distinct trophic habits; (3) search for signatures of positive selection in these genes; and (4) examine the expression of these genes in transcriptomes of larvae and females from different species, using already available RNA-seq datasets. (AU)